Sewage treatment apparatus



'Sept 8, 1942- A. C. DuRDlN, JR 2,295,391

l SEWAGE TREATMENT APPARATUS Filed Deo. 28, 1959 2 Sheets-Sheet l Il* lY' 1 N www l I No i N HMM m m .4 1 l f :1: fxmmmm\ v Avawmv Av/AX/ASept. 8, 1942. A. c. DURDIN, JR

sEwAGE TREATMENT APPARATUS Filed Dec. 28, 1959 zslheets-sheer '2Patented Sept. 8, 1942 UNITED STATES PATENT OFFICE s'EwAGE TREATMENTAPPARATUS Augustus C. `D'urdin, Jr.; Chicago, Ill.

Application December 28, 1939, Serial No. 311,375

` (ci. 21osi 8 Claims.

This invention'- relates to sewage treatment apparatus and particularlyto mechanical aerators of the general type frequently employed in thepurification of sewage in accordance with the activated sludge process.

The activated sludge process may brieiiy be described as comminglingactivated sludge, derived as will be hereinafter described, with in.coming sewage. to agitation and thoroughaeration. The agitation preventssettling and the aeration maintains a supply of oxygen throughout theliquid, which insures biological changes ofia purifying nature. Thefinal result of' the treatment, which may occupy, for example, aroundfive or six hours, is a liquid which settles quite readily, yielding apurified etlluent which may be turned into natural water courses withoutobjection, and a sludge of flocculent nature which is disposed of invarious ways. It is part of this sludge which is mixed with the incomingsewage as mentioned at the beginning of the description of this process.

The activated sludge process is commonly practiced in two types ofinstallations. One type of installation comprises an elongated tank ortanks through which the liquid is passed, 'the aeration air beingadmitted through porous aerators. In another type of installationmechanical aerators are employed. The mechanical aerator is such that itcauses the liquid to circulate rapidly within the tank, aeration beingeffected by the projection of the liquid through the air or, in somecases, by the active admixture of the air and the liquid. Thesemechanicalv aerators are normally driven by an electric motor and inactual practice it frequently happens that the motor becomes overloadedafter a certain period of operation.

One of the principal objects of the invention is to provide improvedmechanism whereby objectionable effects, due to such overloading, are

' obviated.

Fig. 3 is a wiring diagram of a further embodiment of my invention.

Referring to the drawings, the reference numeral Ill designates anaerator tank which may be supplied witha mixture of sewage and activatedsludge ythrough a channel Il. The tank may discharge through a channelI2 into a similar tank, not shown. It will be understood that The mixedliquor is subjected vflow pipe I4 which is provided at its lower endwith a iiared outlet member I5.v A conical member I6 projects into theared outlet member I5 f and is located in spaced relation thereto toprovide forA the efllux of the liquid descending through the tubev I4.The flared outlet member I5 rests upon projections I1 which are integralwith the conical member I6.

The upper end of the downow pipe I4 is supported by means of stays I8which are anchored to the walls of the tank. At its upper end thedownilow pipe I4 carries an impeller section I9 which,`in turn, supportsthe mixing chamber 20 of substantially greater diameter than theirnpeller section I9. The mixing chamber 20 comprises a lower frustroconical portion 2I which carries an upwardly extending cylindrical wall22 which formsthe upper part of the mixing chamber. The wall 22 isprovided with a plurali/ty ofopenings 23 which communicate with troughs24 4 tion. It is connected to the wall 22 around its greatercircumference at a height immediately below the openings 2,3.v Thetroughs 24 are located so that they are supplied with liquid from thecontents of the tank, that is, they are arranged so that their lowerportions are below the normal liquid level of the tank. The liquid flowsinwardly into the annular space 26 provided between the upper part ofthe wall 22 and the Weir plate 25, and it flows through openings in theweir plate down into the lower part of the mixing chamber 20 during thenormal operation tank. In normal r forward operation the mol tor 29operates the impeller so as to force liquid downwardly through tube |4,which causes a circulation around the tank I0. The liquid being receivedat points remote from the center by means of the troughs 24,short-circuiting of the liquid is prevented.

When the impeller 21 forces the liquid downwardly, liquid flows inthrough the slots of the weir plate 25 and splashes downwardly into themixing chamber 28 wherein it is thoroughly admired with air. The air ischurned up by the impeller 21 and is nally distributed throughout theliquid with the result vthat the air in the form of small bubbles is, toa great extent, forced down through the pipe |4 and rises up through theliquid in the tank IU around the pipe |4. This intimate treatment of theliquid with the air maintains a high rate of supply of oxygen to theliquid so that the biological changes of aerobic type may continuewithout interruption during the course of the treatment.

Referring to Fig. 2, the motor 29, which may suitably be a three-phasealternating current motor, is supplied with two power lines 32 and 33and a common power line 34. The power lines 32 and 33 contain thewindings of relays 35 and 3S, respectively, which are adapted, whenenergized suciently, to open one or other of the associated overloadswitches 31 and 38, respectively.

The power line 34 is connected to the power line 32 through the winding39 of a. timing'relay, a normally closed switch 40, and a normally openswitch 4|` The power line 34 is also connected to the power line 32 by aparallel circuit which includes a normally closed stop switch 42, anormally open switch 43, and a winding 44 of a relay which, whenenergized, is adapted to close switches 4| and 43.

The common sides of the winding 44 and switch 43 are connected to thethree-point make switch 45. One side of the switch 45 is connected tothe stop switch 42, to the other side of the switch 43, to one side of anormally open switch 46, and to one side of the normally open switch 41.The three switches 45, 46 and 41 are arranged in parallel, their commonside being connected to a winding 48 of a relay which is adapted, whenenergized, to close the switch 46 and open the Switch 40. The winding 48is in series with the switches 31 and 38.

Each of the power lines 32, 33 and 34 includes a switch 49, 50 and 5|,respectively. These switches are normally open and are adapted to beclosed by the winding 48 when energized. The switches being in therelation shown in Fig. 2, operation of the motor is started by closingthe switch 45. This completes a circuit from power line 34 throughswitches 31, 38, winding 48, switch 45, andswitch 42 to power line 32.This circuit energizes the winding 48, closes the switch 46, opens theswitch 48 and closes the three switches 49, 50 and 5|. The closing ofthe latter switches puts the motor in operation. The closing of Jthethree-contact switch 45 also completes a circuit from power line 34through winding 44, switch 45 and switch 42 to power line 32.

The energization of the winding 44 closes the ,ergization of the winding44.

switches 43 and 4| and holds these switches closed during the continuedoperation of the motor. This results from the fact that the energizedwinding 44 maintains the switch 43 closed and that the circuit throughthis winding is completed through the closed switch 43 and the normallyclosed stop switch 42. When the stop switch 42 is manually opened, thewinding 44 is deenergized and switch 43 opens so that the closing of theswitch 42 does not result in the en- This energization can only occur bythe closing of the switch 45, the switch 42 being closed. The winding 48remains energized, since a circuit is completed through switch 31,switch 38, winding 48, closed switch 45 and switch 42. Opening the stopswitch 42 results in the deenergization of the winding 48 and theopening of the switches 49, 50 and 5|.

In the event that the motor is overloaded, one or other of the switches31, 38 is opened. This also results in the deenergization of the winding48 and the stoppage of the motor. As a result of the deenergization ofthe winding 48, the switch 46 opens, the switch 40 closes, and theswitches 49, 50 and 5| open. The opening of one or other of the switches49 and 50 results in the closing of the switch 31 or 38 associated withthe winding 35 or 38, respectively. A circuit is then completed throughwinding 39, closed switch 40 and closed switch 4|. As a result of theenergize.- tion of the winding 39, theswitch 41 is closed after a delayprovided in known manner, for example, by a slug on the winding 39.Consequently, the motor stops and after a short delay resumes operation.`The resumption results from the closing of the switch 41 whichre-energizes the winding 48 which, in turn, opens the switch 40 andcloses the switches 46, 49, 50 and 5| so that the motor is again putinto operation.

In the embodiment of the invention shown in Fig. 3, means are providedwhereby the motor is not only arrested on overload, but is subjected toa period of reverse operation. In this embodiment of the invention powerlines 32, 33 and 34 are connected respectively to three poles 55, 56 and51, respectively, of the motor when the switches 52, 53 and 54 areclosed. When, however, the switches 58, 59 and 60 are closed, the powerlines 32, 33 and 34 are connected to the poles 51, 56 and 55,respectively.

The overload windings 35 and 36 are associated with switches 31 and 38,as in the previously described embodiment. The power line 32 isconnected to one side of the switch 4| and to one side of the switch 42,as in the previously described embodiment. The power line 34 isconnected to one side of the winding 39 of the time delay relay, as inthe previously described embodiment. The power line 34 is also connectedto two switches 31 and 38 which are arranged in series. The power line34 is also connected to one side o1' the winding 44 whichcooperates withthe two switches 43 and 4|, as previously described.

The other side of the winding 44 is connected to one side of the switch43 and to the three-point make switch 45 which is the start switch. Theother side of the switch 43 is connected to one side of the switch 42,to one point of the switch 45 and to one side of the switch 46. Thethird point of the switch 45 is connected to the winding 48, to theother side of the switch 46 and to a contact 6| of the switch 41.

The other side of the winding 48 is connected to one side of the switch38 and t0 one side of the winding 62. The other side of the winding 62is connected to a contact 63 associated with the switch 41. The otherside of the winding 36 is connected to one side of a switch 46. vTheother side of the switch 46 is connected to contacts 64 is closed. Thenormally open switches 46, 62, 63

and 64 and the normally closed switches 46 and 66 are controlled by thewinding 46. 'I'he normally open switches 66, 56 and 66 are controlled bythe winding 62. The switch 41 normally connects the contacts 63 and 64.When the winding 36 is energized, this connection is opened and thecontact 6I is connected to the contact 66. It will readily be understoodthat, as in the Dreviously described embodiment, the winding 36 isarranged to cooperate vwith the switch 41 so as to provide a delayrelay.

The operation is as follows: To start the maacteristically differentways. According to the first method of operation, the impeller 21 ischine the switch 45 is momentarily closed. This y results in theenergizaticn of the winding 44 and the closing of the switches 4I and43. These switches remain closed until the switch 42 is putting themotor into operation. The winding;

46 remains energized, since it holds the switch 46 closed. Owing to theopen condition of the switches 46 and 66 and the disconnection betweenthe contacts 6i and 65, the windings 62 and 36 are not energized.

It will be noted that when the starting switch 46 is closed, the switch61 is opened and consequently the windings 36 and 62 cannot be energizedwhen the starting switch is closed. When the switch 61 is closed, theswitch 66 is open so that the switches 56, 56 and 66 remain open,whereas the switches 52, 63 and 64 are closed to provide drive in theforward or normal direction.

The operation continues until one or other'of 'the windings 35 or 36draws excessive current,

whereupon one or other of the switches 31, 36 opens. When this occursthe winding 46 is deenergized, the switches 46, 52, 63 and 54 open andthe switches 46 and 66 close. As a result of the closing of the switch66 a circuit is completed through switches 31 and 36 (which immediatelyclose on the cessation of the overload), the winding 62, switch 41 andswitches 66, 61 and 4I. Consequently, the winding 62 is energized andthe switches 66, 66 and 66 are closed. The motor is consequently drivenin the opposite direction.

At the end of a short period, the time delay relay switch 41 moves outof engagement with the contacts 63 and 64 into engagement with the conyWhen this delayed movement oc- `means for operating the impeller 31 intwo chardriven in the forward direction so as to cause the liquid tocirculate down the pipe i4. The incoming liquid enters the troughs 24and spillsl over through the orifice plate 25 into the chamber 26, beingthoroughly mixed withy the air in so falling.

Furthermore, the impeller 21 thoroughly churns the liquid and airtogether and forces the mixture downwardly through the pipe I4.

When overload occurs, the motor 26 may be arrested when equippedaccording to the wiring diagram of- Fig. 2. After a short interval oftime the motor starts again. During that short interval `of time theliquid iills into the chamber 26 and the eddy currentsfor otherphenomena which overloaded the drive are given time to terminate. Themotor 26 starts under low load owing to the high liquid level in thechamber 26, and the rapid longitudinal movements of the liquid withinthe pipe I4 during starting and stopping contribute greatly to the'abolishing of the overloading condition.

When the sewage treatment apparatus is connected according to the wiringdiagram of Fig. 3.

tions which cause the overload. Furthermore,`

this reversal `pumps liquid through the orifice plate 26 in reversedirection and also causes the liquid to flow outwardly through thetroughs 24. Consequently, any iioating debris which tends to congregateadjacent the orifice plate 25 or in the troughs 24 is removed from theselocations. At the same time rags and other debris which may have becomeentangled with the blades of the impeller 21 are removed therefrom.

Although the invention has been disclosed in connection with thespecific details oi' preferred embodiments thereof, it must beunderstood that such details are not intended to be limitative of theinvention except in so far as set forth in the accompanying claims.

Having thus described my invention,'which I I claim as new and desire tosecure by Letters Patent of the United States is:

1. Apparatus for treating sewage comprising a tank, propelling means insaid tank for circulating and aerating sewage liquid therein, powermeans for driving said propelling means, means responsive to overload ofthe propelling means for terminating the drive thereof, and automatictil) means'for causing resumption of said drive after a definite periodof stoppage.

2. Apparatus for treating sewage comprising a tank, propelling means insaid tank for circulating and aerating sewage liquid therein, powermeans for driving said propelling means, and means responsive tooverload of the propelling means for reversing the propeller means.

3. Apparatus for treating sewage comprising a tank, propelling means insaid tank for circulating and aerating sewage liquid therein, anelectric motor for driving said propelling means, means responsive tooverload current for stopping the motor, and automatic means for causingresumption of the operation of said motor.

4. Apparatus for treating sewage comprising a tank, propelling means insaid tank for circulating and aerating sewage liquid therein, anelectric motor for driving said propelling means, and means responsiveto overload current for reversing the motor and said propelling means.

5.v Apparatus for treating sewage comprising a tank, a vertical pipe insaid tank, propelling means adapted to cause liquid in the tank tocirculate through said pipe, an electric motor driving said propellingmeans, means controlled by overload of said motor for stopping saidmotor and automatic means for causing resumption of the operation ofsaid motor.

6. Apparatus for treating sewage comprising a tank, a vertical pipe insaid tank, propelling means adapted to cause liquid in the tank tocirculate through said pipe, an electric motor driving said propellingmeans, and means controlled by overload of said motor for reversing saidmotor and said propelling means.

7. Apparatus for treatngsewage comprising a tank, a vertical pipe insaid tank, propelling means adapted to cause liquid in the tank tocirculate through said pipe, an electric motor driving said propellingmeans, means controlled by overload of said motor for reversing saidmotor and said propelling means, and automatic time delay means forcausing said motor and said propelling means to resume operation intheir normal directions.

8. Apparatus for treating sewage comprising a tank, a vertical pipe insaid tank, propelling means adapted to cause liquid in the tank tocirculate through said pipe, an electric motor driving said propellingmeans, means controlled by overload of said motor for stopping saidmotor, and time delay means for causing said motor to resume operation.

AUGUSTUS C. DURDIN, JR.

